Marine erosion rates and coastal morphology of reef limestones on Grand Cayman Island, West Indies

Abstract

Direct measurements of surface lowering, using the micro-erosion meter technique, have been obtained from Pleistocene and Tertiary limestones in subtidal and intertidal environments on Grand Cayman Island, West Indies. Overall, erosion rates averaged 0.99 mm yr-1; however this figure conceals the fact that the mean erosion rate on open coasts (X=2.77 mm yr−1) was over six times greater than the rate on reef-protected shores (X=0.45 mm yr−1). On lagoonal rocky coasts abrasion and biological action appear to be the dominant erosional processes, but on coasts exposed to high wave surf, bioconstruction dominates over bio-erosion and surface erosion is slight (X=0.17 mm yr−1). Thus, the magnitude and relative importance of physical, chemical and biological erosion processes differ from one locality to the next with variations in coastal exposure and between reef areas with changes in tidal range and wave regime.